This application claims the benefit of German patent applications 10009085.0 filed Feb. 25, 2000, and 10051997.0 filed Oct. 20, 2000, herein incorporated by reference.
The present invention relates to a method and apparatus for the cross-winding of a yarn onto a rotationally driven tube to form a yarn bobbin.
German Patent Publications DE-GM 74 37 800 [utility model] and DE 23 28 828 C2disclose the formation of a yarn reserve on winding bobbins with the aid of a traversing auxiliary yarn guide. The auxiliary yarn guide is pivotable to lift the yarn during an upward pivoting motion out of the yarn guide executing a traversing motion in order to form the desired reserve windings or waste windings on the bobbin tube outside of the traversing range of the yarn guide. A reverse pivoting of the auxiliary yarn guide brings the yarn back into the grasping range of the yarn guide where the yarn is grasped again by the yarn guide upon its traversing motion and is wound further into a cross-wound bobbin.
Such devices are suitable only in a very limited manner or not at all suitable for the problem of transferring the yarn to the yarn guide of the winding head after a yarn interruption and after a subsequent reestablishing of the yarn connection at the work station of a textile machine. In such case, the transfer of the yarn does not take place in coordination with the motion of the yarn guide and, thus, the yarn can be held for a while at one and the same location of the bobbin and can be deposited in a fairly great number of superimposed windings. The superimposed localized yarn windings that result thereby can cause problems during the unwinding of the yarn from the cross-wound bobbins.
German Patent Publication DE 39 30 136 A1 teaches coordinating the motion of the yarn to be transferred and the traversing motion of the yarn guide with one another in such a manner that the transfer of the yarn and the yarn guide arrive essentially simultaneously at the transfer point to the yarn guide and execute the yarn transfer while the yarn guide is in the traversing motion. Although considerable expense is necessary for the construction and regulating technology needed for this transfer, an exact coincidence in time of the arrival of the yarn and of the yarn guide at the transfer point is still not necessarily assured with this device.
In the winding of conical cross-wound bobbins disclosed in German Patent Publication DE 24 54 916 C2, the yarn to be wound onto the tube after a bobbin change or after a yarn break is first held by an auxiliary yarn guide and then taken over after being released by the yarn guide when the latter is moving in the direction of travel toward the smaller bobbin diameter. The raising and lowering of the auxiliary yarn guide takes place by means of a relatively complicated actuating mechanism comprising several pivot levers. The curved yoke-shaped auxiliary yarn guide and actuating mechanism are designed in such a manner that they take up a relatively large amount of space, in particular in the vertical direction, and thus can cause problems on the front side of the winding head, which significantly limits the possibilities of using this system.
The methods and devices disclosed in German Patent Publications DE 24 54 916 C2, DE 39 30 136 A1, DE 23 28 828 C2 and DE-GM 74 37 800 share the significant disadvantage that the traversing yarn guide takes over the yarn to be wound onto the bobbin after it has been released from the auxiliary yarn guide during its back-and-forth traversing motion. This manner of operation entails the danger that the yarn will not be threaded as intended into the yarn guide and will not be entrained in a properly threaded state but rather may be grasped at a position of the yarn guide that is not intended for receiving the yarn and therefore may instead be pushed in front of the yarn guide over the lateral edge of the cross-wound bobbin. This can cause yam breaks and even windings off the bobbin tube onto the supporting tube plate of the winding station which windings can only be removed by a time-consuming intervention by operating personnel. The problem can not be solved even by relatively expensive monitoring and control measures for the yarn guide and the yarn transfer device like those described, e.g., in German Patent Publication DE 39 30 136 A1. Rather, the yarn and yarn guide are merely allowed to arrive essentially at the same time at the transfer point or care is taken that the yarn arrives at least slightly before the yarn guide and in no case after the yarn guide. The danger of the above-cited disadvantages due to an undesired shifting of the yarn over the bobbin edge is present precisely upon an arrival of the yarn in front of the yarn guide or when it is being held ready for the yarn guide executing the traversing motion.
It is therefore an object of the present invention to address these problems with an improvement of the known winding methods and apparatus for transferring a yarn to a traversing yarn guide.
The invention addresses this problem by an improved method and apparatus for cross-winding of bobbins in a textile machine, such as a spinning or winding machine, of the general type comprising a plurality of winding heads each have a traversing yarn guide movable back and forth relative to a bobbin for cross winding of a yarn onto the bobbin and an auxiliary yarn guide movable between an active position for holding the yarn in a raised position out of the traversing yarn guide and an inactive resting position wherein the yarn is positioned to be taken by the traversing yarn guide to be wound onto the bobbin. According to the present invention, after a yarn interruption, such as a yarn breakage, the back and forth movement of the traversing yarn guide is stopped and the interrupted yarn is reconnected, the reconnected yarn is guided by the auxiliary yarn guide into an initial position relative to the traversing path of the traversing yarn guide wherein the auxiliary yarn guide is in the active position, and the yarn is then lowered into the traversing yarn guide by moving the auxiliary yarn guide from the active position into the inactive resting position before the traversing yarn guide is restarted. In the present apparatus, a control device is provided to control actuation of this sequence of steps.
In this manner, a reliable threading of the yarn during its takeover by the traversing yarn guide is achieved in a simple manner and with relatively low expense by the present invention and advantageously avoids an undesired pushing of the yarn in front of the yarn guide beyond the bobbin edge.
The lowering and the take-up of the yarn preferably take place after the drive of the cross-wound bobbin has started and a brief time delay has elapsed after the beginning of the rotation of the cross-wound bobbin. Alternatively, the lowering and the take-up of the yarn can advantageously take place after a set number of revolutions of a friction roller driving the cross-wound bobbin has been achieved. The number of yarn windings wound on the bobbin during the standstill of the traversing yarn guide can thereby be kept extremely small. Localized bands of yarn windings that could result in problems during the unwinding of the cross-wound bobbins are avoided.
The auxiliary yarn guide can preferably pivot between the active position and the rest position. This can reduce the space requirement to a minimum in that the pivot shaft of the auxiliary yarn guide can be located at a very small interval from the traversing yarn guide whereas on the other hand, for example, any type of simple crank system suffices to pivot the auxiliary yarn guide. In particular, the auxiliary yarn guide can be attached to a shaft that can pivot back and forth by means of a pneumatic cylinder which is pivotably mounted to operate the shaft via a pivot lever. The pivoting motion is initiated by the afore-mentioned control device.
In an advantageous embodiment of the device in accordance with the present invention, the mass to be moved can be kept very small and the change from the active position into the rest position of the auxiliary yarn guide can be carried out extremely rapidly. As a consequence, the time required for aligning the yarn in the start position and for the lowering and the take-up of the yarn by the traversing yarn guide can be kept extremely short. In such an extremely short time only a few windings, e.g., 1 to 3 windings, are deposited, so that no localized yarn bands are produced by the winding of the yarn on an unchanging location on the cross-wound bobbin that might cause problems during unwinding.
It is advantageous if the auxiliary yarn guide can pivot in the direction of the traversing yarn guide into its rest position. In addition to an extremely small space requirement and practically no hindrance at the winding head, only a very small pivot angle must be overcome for such a pivoting motion. Moreover, the pivoting motion is supported by the yarn tension. As a consequence, the time delay before restarting of the traversing of the yarn can be held advantageously short.
Preferably, in embodiments in machines and methods for the winding of conical bobbins, the control device is designed such that the traversing yarn guide initially moves after the yarn interruption toward the bobbin end of the greater diameter, whereby the yarn is maintained tautened thereby preventing the yarn from being able to pull itself back out of the traversing yarn guide.
The invention makes possible in a simple manner a reliable take-up of the yarn by the traversing yarn guide after a yarn interruption without disadvantageous winding bands having to occur as in the prior devices described above.
The invention is described in greater detail in the following specification with reference made to the accompanying drawing figures.